1. Field of the Invention
The present invention relates to safety ski bindings comprising a movable plate adapted to clamp the relevant ski boot, and detachably secured to the ski by retaining means engaging the toe and heel ends of the ski boot.
One of said retaining means has a somewhat passive function. The other retaining means comprises a movable retaining bolt associated with a resilient locking mechanism and adapted to engage a notch or cavity formed at the registering end of said movable plate.
The arrangement is such that the resilient locking mechanism is capable of holding the plate against any movement when efforts of limited magnitude and duration are exerted thereagainst, while permitting on the other hand the withdrawal of said retaining bolt in order to release said plate when abnormally high efforts are exerted on the skier's leg or foot. However, this plate should advantageously be released not only in case of torsional stresses tending to rotate the plate in a plane parallel to the top surface of the ski but also in case of upward straining or stretching efforts tending to tilt the plate forwards or backwards. It is also necessary that this release can take place in case of compound movements involving a rotational movement combined with a stretching movement.
2. Description of the Prior Art
In certain known devices of relatively simple design the retaining bolt thus provided can simply slide in the longitudinal direction and a single spring constantly urges said bolt in engagement with ramp or cam faces provided on the registering end of the movable plate in order to hold this plate against movement in its normal position. However, in case of major torsional or stretching efforts, the movable plate can pivot or tilt, thus pushing back the retaining bolt.
In other devices of the same type, the retaining bolt is adapted to pivot in all directions due to the provision of a ball and socket device, a single spring constantly urging said bolt to its normal position while permitting its pivotal movement in the desired direction when abnormal efforts are exerted.
However, in both cases the solution thus proposed is not fully satisfactory for it requires that the resilient force counteracting the plate release differs considerably according as the release movement is a rotational one or an upward or lifting movement, for instance in case of forward or backward fall. In fact, in the first case the resistance should be considerably lower than in the second case, in a ratio which may for example be of the order of 1 to 3. Now this ratio must remain unchanged irrespective of the "hardness" of the setting or adjustment of the mechanism.
Besides, in case of rotational release the resilient retaining mechanism must remain in operative engagement with the movable plate during the longest possible stroke, before the plate is actually released. In fact, if the torsional effort having caused this movement remains of limited value and is exerted only during a reduced or limited time period, the resilient mechanism can still restore the ski boot to its normal skiing position without fully releasing it.
This will avoid too frequent untimely releases of the ski boot. Therefore, this will also deter the users from making too "hard" or tight settings, which might prove very dangerous in actual practice.
To meet these various requirements, certain known ski bindings of the type considered herein are so designed that the two type of movements likely to be performed by the movable bolt are checked or controlled by two separate resilient mechanisms capable of exerting resilient resistances of respective different values against the rotational release and the upward extension release, respectively. However, these known mechanisms are particularly complicated and therefore expensive.